1. Field of the Invention
The present invention relates to a microwave oven, and more particularly to an even heating apparatus for a microwave oven capable of evenly applying microwaves emitted from a magnetron to food by providing an antenna array plate inside a heating chamber thereof.
2. Description of the Prior Art
With reference to FIG. 1 illustrating a microwave oven according to the conventional art, the microwave oven includes a box-shaped heating chamber 1 on an internal portion of which is mounted a magnetron 2 which emits microwaves.
Outside a side wall 3 of the heating chamber 1 there is vertically provided a wave guide compartment 4 for guiding microwaves emitted from the magnetron 2. Through the side wall 3 there are formed a plurality of slots 5 for introducing the microwaves therethrough. A table rotating motor 6 is provided below the bottom of the heating chamber 1. A rotation table 7 is mounted extending from the bottom of the heating chamber 1. On the upper surface of the rotation table 7 there is provided a tray 8 for placing food thereon.
An agitation motor 9 is mounted atop the heating chamber 1. An agitation fan 10 is mounted on a shaft of the motor 9 extending downwardly from a ceiling of the heating chamber 1 for thereby agitating the microwaves introduced through the slots 5 into the heating chamber 1.
FIG. 2 illustrates an imaginary perspective view of the chamber 1 and is provided to denote respective dimensions L1, L2, L3 of the heating chamber 1.
The operation of the thusly constituted microwave oven according to the conventional art will now be described.
First, when current is applied to the magnetron 2, microwaves are emitted from the magnetron 2, and at the same time the rotation table motor 6 and the agitation motor 9 are activated.
The microwave energy emitted from the magnetron 2 is guided along the wave guide compartment 4 and introduced through the slots 5 into the heating chamber 1. Then, the microwave energy flowing into the heating chamber 1 is rendered to a variety of resonance mode frequencies in accordance with rotation of the agitation fan 10, for thereby heating the food on the tray 8.
At this time, the food being rotated on the tray 8 shows a different aspect depending on the size or kind of food in terms of a heating degree.
With reference to FIGS. 3A through 3C, the food heating degrees will now be described.
FIG. 3A is a spectrum graph illustrating a case in which respective dimensions L1, L2, L3 of the heating chamber 1 are respectively less than a wave length .lambda..sub.m of an oscillation frequency outputted from the magnetron 2 and it shows that because there do not occur any resonant modes the food in the chamber 1 is not evenly heated.
Further, FIG. 3B is a spectrum graph illustrating a case in which respective dimensions L1, L2, L3 of the heating chamber 1 are respectively nearly equal or equal to a wave length .lambda..sub.m of an oscillation frequency outputted from the magnetron 2, wherein because there exists only a single resonant mode the food in the chamber 1 is heated only in a particular portion thereof.
Still further, FIG. 3C is a spectrum graph illustrating a case in which respective dimensions L1, L2, L3 of the heating chamber 1 are respectively longer than a wave length .lambda..sub.m of an oscillation frequency outputted from the magnetron 2, wherein because there exist a plurality of resonant modes the food in the chamber 1 is heated in a confined portion of the food.
However, in consideration of a relation between respective dimensions and resonant modes, when the respective dimensions of the heating chamber 1 are less than or almost equal to a wave length .lambda..sub.m of an oscillation frequency outputted from the magnetron 2, the food in the chamber 1 is not evenly heated regardless of the rotation of the agitation fan 10 and the table 7.
Further, when the respective dimensions of the heating chamber 1 are longer than a wave length .lambda..sub.m of an oscillation frequency from the magnetron 2, heating of the food in the chamber 1 is confined to a particular portion thereof in terms of an even heating, thereby making it difficult to heat food at a constant heating rate irrespective of the size, weight and the like of the food.